This invention relates to a water soluble lubricious coating for a medical device such as a catheter assembly.
Catheters are used in surgical procedures for insertion into blood vessels, urethra, or body conduits during such procedures as coronary angioplasty, stent delivery and placement for the opening of occluded or blocked blood vessels, for urological and reproductive surgeries, and to deliver biologically compatible fluids, such as radiologically opaque fluid for contrast x-rays to precise locations within the body.
Depending on the procedure involved, catheters may be one of several different types including an over the wire, a single operator exchange or a fixed wire catheter assembly.
Over the wire catheters may be used as guide catheters during coronary angioplasty, for instance. The guide catheter provides access to the area in which the stenosis or blockage may be found, and provides support for the treatment catheter which often includes a balloon dilatation system wherein a dilatation balloon is delivered to a site of stenosis in an artery and is used to alleviate the stenosis.
In operation, the guide catheter is introduced over a guide wire through a previously placed introducer sheath and advanced through a blood vessel to the location of a stenosis. The guide wire can then be removed.
Other procedures may involve the introduction of other medical devices at precisely specific bodily locations including the delivery of stents, stent-grafts, grafts, vena cava filters, other expandable medical devices, and so forth.
During these procedures, the catheters must be able to traverse tortuous pathways through blood vessels to the stenosis in a manner as atraumatic to the patient as possible. It is therefore desirable to make insertion through the patient in such a way to limit the insertion time and discomfort as much as possible.
A common problem which occurs in catheter assemblies is friction or adhesion between various parts which periodically come into contact with one another during the medical procedure. For instance, friction can occur between the guide catheter and guide wire, between the introducer sheath and the guide catheter, or between the guide catheter and the balloon catheter, for instance, and may increase the difficulty of insertion, cause loss of catheter placement, and result in discomfort or damage to the patient. It is therefore desirable to improve the moving relationship between the various parts of the catheter assemblies.
The materials from which catheters are produced are typically polymeric or metallic in nature, and in general, are inherently non-lubricious. When these non-lubricious materials come into contact, friction occurs. Medical device manufacturers have used various approaches to reduce the coefficient of friction between these surfaces.
Hydrophobic coatings have been used to impart lubricity to medical devices including silicone based lubricants, glycerine or olive oil. These coatings have been known to wash off when exposed to an aqueous environment, lose initial lubricity rapidly, and lack abrasion resistance. Residual amounts of silicone have also been known to cause tissue reaction and irritation in patients. The loss of lubricity can lead to discomfort during insertion into a patient, and damage to blood vessels and tissues due to frictional forces during insertion or removal of the device. Examples of silicone based lubricants include polysiloxanes and modified polysiloxanes. Often they include a polar group which may be an aminoalkyl or carboxyalkyl terminating group. U.S. Pat. No. 5,084,315 to Karimi et al. issued Jan. 28, 1992 discusses the problems with migration and beading.
U.S. Pat. No. 5,266,359 to Spielvogel issued Nov. 30, 1993 describes a lubricating composition for a medical device which includes an emulsion of a noncuring polysiloxane, a surfactant and water. The surfactants are copolymers of polysiloxane and polyoxyethylene which are reactive and when cured, adhere to the surface. While Spielvogel teaches a method of application which does not utilize solvent, the problems associated with silicone based lubricants remain.
U.S. Pat. No. 5,272,012 to Opolski issued Dec. 21, 1993 describes a method for providing a medical apparatus with a protective lubricious coating comprising providing a coating solution which contains a protective compound such as a urethane, a slip additive such as a siloxane, and optionally, a crosslinking agent for the protective compound such as polyfunctional aziridine, coating the solution onto a surface of a medical apparatus and allowing the coating to set. The protective compound binds the slip additive such that domains of the slip additive are exposed in the formed layer. The coating solution may also contain a crosslinking agent. The protective compound binds the slip additive such that domains of the slip additive are exposed in the formed layer. The coating solution may also contain a crosslinking agent. The protective compound preferably has functional moieties capable of crosslinking to other moieties within the protective compound and with moieties derived from the medical device.
Another approach for reducing the coefficient of friction is to add a layer of a low friction material such as polytetrafluoroethylene, hereinafter PTFE and commonly known by the tradename of Teflon(copyright). For instance, PTFE may be added as an inner layer of an internal catheter lumen to reduce friction between the guide catheter and the treatment catheter, for instance. The problem with the use of this inner layer of PTFE is that it requires a separate extrusion process, and also requires etching. Adhesion is also generally a problem between the PTFE and the polymeric catheter material as well. U.S. Pat. No. 5,647,846 to Berg et al. solved these problems through the use of a geometrically configured inner surface of the inner layer of a guide catheter, achieving low friction properties through geometry, rather than through the use of a lubricious polymer, thereby eliminating the need for the lubricious polymer. Berg et al. however, discusses forming the inner layer of a lubricious polymer, such as PTFE, or alternatively, coating the inner surface with a lubricant such as silicone.
Hydrophilic compounds have also been used to impart lubricity in medical devices. Such compounds are biocompatible or blood compatible, and are more readily discharged from the body and have less of a tendency to cause tissue irritation. However, because of the hydrophilicity, It is also more difficult to retain such coatings on the surface of the medical device throughout the procedure. U.S. Pat. No.5,509,899 to Fan et al. issued Apr. 23, 1996 describes a lubricious coating for a medical balloon and catheter wherein the balloon is tightly wrapped and folded upon itself tortuously and tightly so that when in contact with each other for insertion into the body, the balloon is free of bridging and adhesion between abutting surfaces. The balloon has a base of a continuous polymeric surface which is expandable from a folded, wrapped configuration with surfaces touching each other. Examples of such polymeric materials include Nylon, Selar(copyright), polyethylene terephthalate, polyethylene or similar materials. These materials may provide excellent balloon stock but are not necessarily sufficiently lubricious to be used by themselves. Therefore, a lubricious, biocompatible hydrogel coating is disposed on the polymeric surface and a thin, lubricious, blood-compatible coating is disposed upon the hydrogel coating and adheres to it to prevent abutting surfaces of folded polymer surfaces from adhering to each other during inflation and also to prevent delamination of the hydrogel coating and/or rupture of the balloon. The blood-compatible coating is polyethylene glycol, methoxy polyethylene glycol or mixtures thereof having a molecular weight between about 100 and 20,000 grams per mole.
U.S. Pat. No. 5,849,368 to Hostettler et al. issued Dec. 15, 1998 describes a process for rendering the surfaces of polymeric plastic or rubber materials, which are intrinsically non-polar or only slightly polar, polar or more polar, and hydrophilic, so that amine-containing functional groups, and ultimately, a durable tenaciously adhering, slippery polyurethane or polyurethane-urea hydrogel coating may subsequently be applied to the polymer surface. The process involves dual plasma-treatment of a polymeric plastic or rubber substrate material such that amine and amino groups are affixed to the substrate surface to make it more hydrophilic and reactive toward the terminal isocyanate groups of the polyurethane or polyurethane/urea prepolymers.
Although each of these methods describes a way in which the coefficient of friction may be reduced, a need still exists for a simple, easy to apply coating which is lubricious and biocompatible, and which has good retention on the surface of the device.
The present inventors have found a hydrophilic lubricant coating for medical devices, and in particular for catheter assemblies, to render inherently non-lubricious surfaces, lubricious, and a method for coating such devices which involves coating the inner surface a tubular member of a medical device. This hydrophilic lubricant coating overcomes the aforementioned problems associated with conventional lubricious coatings, and the problems associated with the use of silicone based lubricants and the addition of polytetrafluoroethylene layers.
This invention relates to a coating for rendering a medical device lubricious. The coating comprises pretreating primer composition, and a hydrophilic lubricious coating. The primer compound comprises substituents that are capable of adhering or bonding to, and improving the retention of the hydrophilic lubricant to the surface of the medical device. One such mechanism through which the primer compound may retain the hydrophilic polymer, is through hydrogen bonding.
This invention further relates to a medical device comprising at least one tubular member having an inner surface and an outer surface. The inner surface of the tubular member is at least occasionally subjected to contact with at least one second surface. The tubular member further comprises a hydrophilic coating disposed on the inner surface. The hydrophilic coating is present to inhibit the inner surface of the tubular member and the second surface from adhering to each other, and reduces the friction caused by movement between the two surfaces. The inner surface may first be pretreated with the primer composition.
The tubular member preferably comprises at least one thermoplastic polymer and the second surface preferably comprises a metal.
The hydrophilic coating may be coated on the inner surface of the tube by injection, or coextrusion.
This invention further relates to a catheter assembly comprising at least one polymeric sheath having an inner surface and an outer surface. The inner surface of the first polymeric sheath is at least occasionally subjected to contact with at least one second surface, and comprises a water soluble coating disposed on the inner surface of the polymeric sheath. The hydrophilic coating is present to inhibit the inner surface and the second surface from adhering to each other.
The polymeric sheath comprises at least one thermoplastic polymeric material. The second surface to which the inner surface of the polymeric sheath comes into contact may be a polymeric material or a metal.
The inner surface of the polymeric sheath may first be coated with a primer of a crosslinkable composition which is readily wettable. This improves the uniformity and shelf stability of the lubricious coating. The water soluble lubricious coating may further comprise Vitamin E to further improve the shelf stability of the coating.
The present invention further relates to a stent deployment catheter assembly having at least one tubular member for retention and release of a stent. The tubular member may be a retractable sheath, or it may be at least one stent retaining sleeve. A hydrophilic lubricious coating is disposed on the inner surface of the tubular member in order to facilitate stent release by reducing the coefficient of friction between the tubular member and the stent.
The lubricious coating of the present invention provides improved lubricity, eliminates migration problems associated with oil based lubricants and eliminates tissue reaction and irritation associated with oil based silicone lubricants.
Furthermore, due to the excellent lubricity, the diameter of the outer sheath of a medical device may be decrease thereby improving performance.